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Itb?

Discussion in 'Engine Building' started by 5speed, Mar 30, 2010.

  1. 5speed

    5speed New Member

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    Got a question..i've got a guy who wants to go with ITB's on a H23 non vtec...i dont know too much about ITB's but you dont need a intake for filter correct? Since each cylinder has it's own throttle body...and we're planning to space it so we can use the stock fuel rail and fuel injectors..but it should be a direct bolt on..plug and play? I've also heard that you should have built motors to run the ITB, but then again i also heard that it's fine if the motor is stock also..either way gotta get it tuned and they should be fine..correct? are there anything else i may need to get in order to run and install the ITB or just the ITB?
     
  2. kelsodeez

    kelsodeez New Member

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    to get any kinds of notable gains, you need to have at least 11:1 compression. also, you dont have to run a filter, but remember that your engine is just a big vacuum and it will suck up everything and anything in the air. at the least, run a mesh screen between the velocity stack and the tb. then large contaminants wont get into the engine.
     
  3. 78civic

    78civic Junior Member

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    NO filter? Just think of it, now there's 3-more big ports to suck junk in your engine..

    If someone wants a set of ITB's, and you have to make the intake anyhow, at least make a decent air cleaner. OR, some little motorcycle 'cone' filters.

    E
     
  4. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Yup, filter each one or build a giant plenum around the intake ports with a filter on the end.
     
  5. kelsodeez

    kelsodeez New Member

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    building a plenum kind of negates the main reason for ITB's. if you create a space that has to be filled with air, it hurts throttle response and ultimately hurts HP. i was thinking about running those nylon booties on my ITB's.
    [​IMG]


    this is ideal to have, but they are pretty pricey.

    [​IMG]

    the cone filters will work well too, but i wont run them because 1. i dont have enough room and 2. i think they are ugly as sin.
     
  6. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Nope, not at all. It'll only hurt if the plenum is too small to supply air to all the cylinders- the same as in a normal single throttle plate build. Your gain is in metering the air at the entrance of each intake runner instead of at at the front of the plenum- that's where you get the response gain and the power gain.
     
  7. kelsodeez

    kelsodeez New Member

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    but i was under the assumption that if you create negative pressure before the intakes, then you are restricting the capacity that the engine is capable of sucking in. it would all come down to how much cfm the engine wants to suck in compared to the enclosure area, the size of the intake inlet and the enclosure's capacity for air.
     
  8. eg6sir

    eg6sir Supa Mod Moderator VIP

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  9. Briansol

    Briansol Admins Admin VIP

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    itb's are a whore to work with. IMO, they should be considered the LAST mod on any list.

    huge cams, huge compressions, all the basic bolt ons, etc etc completed.
    THEN and only then consider itb's.

    then, cry when you spend $2k on the dyno trying to get them to idle....
     
  10. K2e2vin

    K2e2vin Senior Member

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    A lot of OE cars have plenums around their ITBs(the Skylines had ITBs with a plenum, 4AGEs, and some BMWs), including sport bikes, and even F1 cars. Plenums do not restrict the engine's ability to pull in air unless, as Cal stated, your plenum is too small. The plenum would not create negative pressure before the intake either; atmospheric pressure is pushing air in and, in some cases, ram-air effect can be utilized. If you think about it, the engine itself is one big plenum.

    ITBs are FAR from plug and play, especially with a open-air(non-plenum) setup.
     
  11. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Just don't build a plenum that introduces any restrictions. :D

    Yup. Do them LAST. And get a hookup on dyno time. I fully intend to exploit ITBs on one of my builds one of these days... access to all the time I want on a dyno is a nice perk. :D

    Yup. Plenum around ITBs = normal. You just don't see them on all these aftermarket ITB setups because the owners want to show off the $$$$ they spent on the minimal gains under the hood.

    :D
     
  12. K2e2vin

    K2e2vin Senior Member

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    Just noticed, but I meant to say the engine bay is one big plenum*
     
  13. kelsodeez

    kelsodeez New Member

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    im just going to run the jenvey air filter with backing plate.
     
  14. Briansol

    Briansol Admins Admin VIP

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    so true. guy i know who ran them on a 270 whp all motor B LOST about 8 hp with itb's over a JG big mouth.
     
  15. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Of course, this isn't necessarily because he used ITBs in general- you can usually gain power when they're sized correctly. They may not have had a runner configuration as good as the intake manifold he replaced.
     
  16. 78civic

    78civic Junior Member

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    I wonder if they run into such problems with all the different motorcycle mfgrs making them on assembly lines..?
    Multiple carbs have been around for decades, and really all you're doing is adding a TPS. They would all be synced for just airflow and spraying water on that particular exhaust port to see if it steamed off like the others. The FI ones you could use EGT sensors for each cyl. Wouldn't that 'tune' it better?

    The Early RS civics had a Kehnin on each cyl and they didn't have high comp or that big of a cam. Or how 'bout the mutli-carbed Datsuns, Porsches?

    I know it sounds like a pain, but i'd like to do a mutliple carb setup also.. It might give me MORE grey hair, but if it was FI that would just drive me nuts.

    E
     
  17. K2e2vin

    K2e2vin Senior Member

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    Far from just adding TPS. Carbs are mechanical so fuel will only flow when there's a pressure difference in the venturi. On the other hand, PGMFI relies on MAP, MAF, and/or Alpha-N(TPS) readings. The issue with this is MAP readings will fluctuate at certain levels(and even stay the same past a certain throttle angle) where MAP/Alpha-N hybrid is a necessity; this is where ITBs become a PITA. First, you'd need your MAP readings as smooth as possible(I've seen many bikes use a "damper" chamber) and figure out the best crossover point(which is not just at WOT btw). Then, you'd need to tune for both.
     
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